Re: Re: LF: Do I need an attenuator on LF RX??

["mike.dennison" <mike.dennison@ntlworld.com>]

Chris. Isn't the 'noise hump' due to the resonance of your antenna? 

Mike

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On 12 Feb 2018 at 16:35, <Chris Wilson> wrote:

Hello Mike,

Thanks  for  the  reply, it actually has 2 (in series) N1BUG band pass
filters in front of it! I have always had this "noise hump" around the
band, I once thought the filter (one...) had cured it, but next time I
looked  it  was  back.   MF  is  lovely and quiet in comparison. i see
exactly the same with a Softrock with or without a BPF.

http://blog.n1bug.com/2017/02/01/2200-meter-softrock-lite-ii/

Monday, February 12, 2018, 4:26:13 PM, you wrote:

> Chris,

> It looks like you have a broadcast station where it shouldn't be (at  
> 132.65kHz) and several other spurious stations in that area, so you  
> may well have unwanted signals within the 136kHz band, especially at  
> night (your recording seems to have been done during the middle of  
> the day). You might improve things by by-passing the pre-amp. It  
> would do no harm just by experimenting with an attenuator but why  
> attenuate and amplify at the same time unless the preamp also  
> provides another function such as matching? It seems the only  
> front-end selectivity on that receiver is a narrow bandpass so you  
> would really benefit from some additional wider filtering, eg an LPF  
> with a cut-off just below the LW BC band.

> Mike, G3XDV
> ==========





--  
Best regards,
 Chris                            mailto:dead.fets@gmail.com